Die assembly

ABSTRACT

MENTS BEING COAXIAL BUT OF DIFFERENT CROSS-SECTIONAL DIMENSIONS TO PROVIDE IN EFFECT A PASSAGE THROUGH THE DIE TAPPERING FROM MINIMUM CROSS SECTIONS NEAR ONE END OF THE DIE TO MIXIMUM CROSS SECTION NEAR THE OPPOSITE END OF THE DIE. MEANS MAY BE PROVIDED FOR APPLYING AND CONTROLLING FLUID PRESSURE SEPARATELY TO THE RESPECTIVE DIE ELEMENT WHEREBY OPTIMUM CONTROL OF THE COLLAPSING OF THE TUBULAR METAL BLANK ABOUT THE MANDREL IS ATTAINED. MEANS ARE PREFERABLY PROVIDED PRESSING THE FLANGES OF THE DIE GENERALLY AXIALLY OF THE DIE ASSEMBLY AGAINST THE HOUSING TO PREVENT LEAKAGE OF PRESSURE FLUID BETWEEN THE FLANGES AND THE HOUSING. SPACED APART STRUTS ARE PREFERABLY PROVIDED WHICH EXTEND GENERALLY AXIALLY OF THE DIE ASSEMBLY BETWEEN THE FLANGES TO PRESS THE FLANGES AGAINST THE HOUSING. THE STRUTS ARE DESIRABLY LONGITUDINALLY EXTENSIBLE TO ENABLE THEM TO EXERT A CONTROLLED DEGREE OF PRESSURE AGAINST THE FLANGES, THEY MAY BE PROVIDED WITH THREADED EXTENSION DEVICES. DESIRABLY HOLLOW PRESSURE TRANSMITTING MEMBERS LIE AGAINST THE FLANGES AND THE STRUTS APPLY PRESSURE AGAINST SUCH MEMBERS.   A DIE ASSEMBLY FOR FORMING A TUBULAR METAL BLANK ON A TAPERED MANDEREL INTO A TAPERED TUBE CONFORMING TO THE TAPER OF THE MANDREL COMPRISING A DIE COMPOSED OF NONMETALLIC PLASTIC MATERIAL CAPABLE OF BEING REPEATEDLY STRETCHED OUTWARDLY AND CONTRACTED BACK TO ITS ORIGINAL FORM, THE DIE HAVING A PASSAGE THERETHROUGH TAPERING FROM MINIMUM CROSS SECTION NEAR ONE END OF THE DIE TO MAXIMUM CROSS SECTION NEAR OPPOSITE ONE END OF THE DIE AND DESIRABLY HAVING OUTWARDLY PROJECTING FLANGES AT ITS RESPECTIVE ENDS, A HOUSING IN WHICH THE DIE IS MOUNTED AND MEANS FOR APPLYING FLUID PRESSURE IN THE HOUSING AGAINST THE OUTSIDE OF THE DIE TO COLLAPSE THE TUBULAR METAL BLANK ABOUT THE MANDREL AS THE TUBULAR METAL BLANK AND MANDREL PASS THROUGH THE DIE. THE FLANGE AT THE LARGER END OF THE DIE PREFERABLY HAS A GREATER TRANSVERSE DIMENSION THAN THE FLANGE AT THE SMALLER END OF THE DIE. THE OUTSIDE DIMENSIONS OF THE FLANGES ARE PREFERABLY SMALLER THAN THE INSIDE DIMENSIONS OF THE HOUSING OPPOSITE THE FLANGES BY AT LEAST ABOUT 6% OF THE MAXIMUM OUTSIDE DIMENSION OF THE FLANGES. THE DIE MAY COMPRISE A PLURALITY OF DIE ELEMENTS ARRANGED SIDE BY SIDE IN CONTACT EACH HAVING A PASSAGE THERETHROUGH, THE PASSAGE THROUGH THE DIE ELE-

F. J. LESKO DIE ASSEMBLY Feb. 13, 1973 4 Sheets-Sheet 1 INVENTOR.

J. LESKO M) {W HIS ATTORNEYS FRANK Filed Jan. 14, 1971 Feb. 13, 1973 F. J. LESKO DIE ASSEMBLY Filed Jan. 14, 1971 4 Sheets-Sheet 2 I6 19 Ti 20 m l W i FIG.2.

INVENTOR FRANK J. LESKO F. J. LESKO DIE ASSEMBLY Feb. 13, 1973 4 Sheets-Sheet 5 Filed Jan. 14, 1971 I NV E NTOR. FRANK J. LESKO BY WW 4,414; 1 744,1 4 JQH LMJ HIS ATTORNEYS F. J. LESKO DIE ASSEMBLY Feb. 13, 1973 Filed Jan. 14, 1971 4 Sheets-Sheet 4 INVENTOR.

J. LESKO B W fiw,

FRANK warm ms ATTORNEYS United States Patent 3,715,904 DIE ASSEMBLY Frank J. Lesko, Phoenix, Ariz., assignor to Reynolds Metals Company, Richmond, Va. Filed Jan. 14, 1971, Ser. No. 106,344 Int. Cl. B21c 3/06 US. Cl. 72-276 13 Claims ABSTRACT OF THE DISCLOSURE A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of nonmetallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die having a passage therethrough tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die and desirably having outwardly projecting flanges at its respective ends, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die. The flange at the larger end of the die preferably has a greater transverse dimension than the flange at the smaller end of the die. The outside dimensions of the flanges are preferably smaller than the inside dimensions of the housing opposite the flanges by at least about 6% of the maximum outside dimension of the flanges. The die may comprise a plurality of die elements arranged side by side in contact each having a passage therethrough, the passages through the die elements being coaxial but of different cross-sectional dimensions to provide in effect a passage through the die tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die. Means may be provided for applying and controlling fluid pressure separately to the respective die elements whereby optimum control of the collapsing of the tubular metal blank about the mandrel is attained. Means are preferably provided pressing the flanges of the die generally axially of the die assembly against the housing to prevent leakage of pressure fluid between the flanges and the housing. Spaced apart struts are preferably provided which extend generally axially of the die assembly between the flanges to press the flanges against the housing. The struts are desirably longitudinally extensible to enable them to exert a controlled degree of pressure against the flanges; they may be provided with threaded extension devices. Desirably hollow pressure transmitting members lie against the flanges and the struts apply pressure against such members.

This invention relates to a die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel in which a die is employed which is composed of non-metallic plastic material, such, for example, as hard and tough nylon, capable of being repeatedly stretched outwardly and contracted back to its original form, the die being mounted in a housing, and means being provided for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the tapered mandrel as the tubular metal blank and mandrel pass through the die. Reinforced nylons sold as Nylafil and Cadco have been found satisfactory for the die. The die may be mounted in position and the tapered mandrel with the tubular metal blank thereon may be pulled or pushed through the die, or the mandrel and blank may be mounted in position and the die traversed therealong. The forming may be accomplished beginning at either end of the tapered mandrel, i.e., the tapered tube may be formed progressively from its smaller end to its larger end or progressively from its larger end to its smaller end. The mandrel and hence the tapered tube formed thereon may be of circular, polygonal or other cross section.The blank formed into a tapered tube may be of ferrous or non ferrous metal but must be sufliciently ductile to respond to the forming operation; an example is aluminum.

Die assemblies as above described have been used in the formation of tapered metal tubes but problems have arisen which have not in all cases been satisfactorily solved, particularly in the forming of tapered metal tubes of relatively great transverse dimension. The dies of non-metallic plastic material have failed, either by being extruded or partially extruded along the tapered metal tube being formed or by being sheared or partially sheared between the tapered metal tube being formed and the housing. Also leakage of pressure fluid between the die and the housing has occurred.

I have solved the problems by redesigning the die to eliminate extrusion of the die along the tapered metal tube being formed and to eliminate shearing of the die between the tapered metal tube being formed and the housing and by providing for firmer mounting of the die in the housing to eliminate leakage of pressure fluid between the die and the housing.

I have found that the die should have a passage therethrough tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die. This form of die of non-metallic plastic material collapses the tubular metal blank about the tapered mandrel as the tubular metal blank and mandrel pass through the die, forming a tapered tube conforming to the taper of the mandrel without extrusion or shearing of the die.

The die of non-metallic plastic material is stretched outwardly or expands in the housing as the portion of the tapered metal tube of relatively great transverse dimension is being formed. The constricted end of the die, i.e., the end of the die of smaller transverse cross section, expands more than the larger end and provision for such differential expansion without undesirable deformation of the die as by unduly crowding or confining it in the casing must be made. The die has outwardly projecting flanges at its respective ends, and I make the flange at the larger end of the die With a greater transverse dimension than the flange at the smaller end of the die. This relative proportioning of the flanges provides for the desired differential expansion of the die. I find that the outside dimensions of the flanges should be smaller than the inside dimensions of the housing opposite the flanges by at least about 6% of the maximum outside dimension of the flanges. For optimum results I make the outside dimension of the flange at the larger end of the die smaller than the inside dimension of the housing opposite that flange by at least 6% of the maximum outside dimension of the flanges and the outside dimension of the flange at the smaller end of the die smaller than the inside dimension of the housing opposite that flange by at least about 8% of the maximum outside dimension of the flanges.

The improved results of my novel shaped die may be obtained by use of a die having a plurality of die elements arranged side by side in contact each having a passage therethrough, the passages through the die elements being coaxial but of different cross-sectional dimensions to provide in effect a passage through the die tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die. I desirably provide means for applying and controlling fluid pressure separately to the respective die elements whereby optimum control of the collapsing of the tubular metal blank about the mandrel is attained.

To prevent leakage of pressure fluid between the flanged die and the housing I provide means pressing the flanges of the die generally axially of the die assembly against the housing. Such means may take the form of spaced apart struts which extend generally axially of the die assembly between the flanges of the die. The struts are desirably made longitudinally extensible, as by providing them with threaded extension devices, to enable them to exert a controlled degree of pressure against the flanges. Hollow pressure transmitting members (in the form of rings when a tapered metal tube of circular cross section is being formed) may be provided which lie against the flanges, and the struts apply pressure against such members, forming what may be termed a spreader cage for the die.

Other details, objects and advantages of the invention will become apparent as the following description of certain present preferred embodiments thereof proceeds.

In the accompanying drawings I have shown certain present preferred embodiments of the invention in which FIG. 1 is a central vertical cross-sectional view with portions cut away illustrating diagrammatically the formation of a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel in which one form of my improved die assembly is employed;

FIG. 2 is an enlarged central vertical cross-sectional view showing the form of my improved die assembly which is illustrated in FIG. 1;

FIG. 3 is a view similar to FIG. 2 showing a modified form of my improved die assembly and showing a tapered mandrel and a tapered tube being formed thereon; and

FIG. 4 is a view similar to FIG. 2 showing a further modified form of my improved die assembly.

Referring now more particularly to the drawings and first to FIG. 1, there is shown a tapered mandrel 2 on which is disposed a tubular metal blank 3, which tubular metal blank is formed or collapsed on the mandrel 2 into a tapered tube conforming to the taper of the mandrel. For purposes of explanation and illustration the mandrel 2 and tubular metal blank 3 may be deemed to be of circular cross section although as above indicated they may be of other cross sections.

It is known to form a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel, but the dies which have been employed for that purpose have not proved entirely satisfactory, particularly in the formation of tapered tubes of relatively large size, for example, tapered tubes four inches in diameter at the smaller end and eight inches in diameter at the larger end which may be used for light poles and similar applications. At the beginning of the operation the tubular metal blank is of uniform diameter from end to end except that its forward end may be deformed or otherwise adapted to pass through the forming die and be gripped by grippers to pull the mandrel and tapered metal blank through the die. Alternatively, the mandrel and tapered metal blank may be pushed through the die, as, for example, by a ram 4. As the mandrel and tubular metal blank pass through the die the tubular metal blank is collapsed about the mandrel so that its inner surface conforms to the outer surface of the mandrel. After completion of the operation the tapered tube is stripped from the mandrel.

Dies used for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel may be made of various materials; I prefer hard and tough nylon which is capable of being repeatedly stretched outwardly and contracted back to its original form. Such material has heretofore been employed for the purpose but the dies have been subject to disadvantages which have been pointed out above. My improved die assembly causes optimum formation of a tapered tube and the die is not subject to deformation or 4 shearing as have been dies previously employed for the purpose.

I employ a housing 5 which in the embodiments illustrated in the drawings is of circular shape about the axis of the mandrel and of U shape parallel to the axis of the mandrel. One side of the housing 5 is open as at 6 and the opposite side has an opening 7 for egress of the mandrel with the tapered tube being formed thereon. In FIGS. 1 and 2. the die proper is designated 8 and has a passage 9 therethrough which as shown in FIGS. 1 and 2 tapers from maximum cross section near the entry end of the die to minimum cross section near the exit end of the die. The die 8 has outwardly projecting flanges at its respective ends, a flange 10 at the smaller end and a flange 11 at the larger end. The die is confined in the housing 5 by a closure member 12 forming part of the housing which has an opening 12a which assists in guiding the mandrel with the tubular metal blank thereon to the die. As the mandrel with the tubular metal blank thereon moves through the die the tubular metal blank is collapsed about the mandrel by the action of the die as shown in FIG. 1.

The die is subjected to fluid under pressure which is admitted into the housing through a pipe 13 and is subject to being exhausted through a pipe 14 having a throttle valve 15 controllable manually or otherwise. The fluid pressure exerted against the die naturally causes some deformation of the die but my improved form of die withstands the deformation and accomplishes in optimum fashion the formation of the tapered tube. The outer peripheries of the flanges 10 and 11 are, as shown in FIGS. 1 and 2, spaced from the surrounding portion of the housing to permit expansion of the die in the housing under pressure. The die will expand more at the smaller end than at the larger end so the outer periphery of the flange 10 is spaced from the surrounding portion of the housing a distance greater than the outer periphery of the flange 11. The outside dimensions of the flanges should be smaller than the inside dimensions of the housing opposite the flanges by at least about 6% of the maximum outside dimension of the flanges. For optimum operation the outside dimension of the flange 11 at the larger end of the die should be smaller than the inside dimension of the housing opposite that flange by at least about 6% of the maximum outside dimension of the flanges and the outside dimension of the flange 10 at the smaller end of the die should be smaller than the inside dimension of the housing opposite that flange by at least about 8% of the maximum outside dimension of the flanges.

The die 8 is mounted in the housing 5 by what may be termed a spreader cage designated generally by reference numeral 16. The spreader cage comprises opposed hollow pressure transmitting devices 17 and 18 which in the illustrated embodiment of the invention are of ring shape although each thereof is divided into two sections, an upper section in the shape of a half ring and a lower section in the shape of a complementary half ring. One of the pressure transmitting devices has spaced thereabout a series of hollow projections 19 and the other pressure transmitting device has spaced thereabout a series of threaded studs 20 each threaded into a nut 21 bearing against one of the'hollow projections 19. Thus the sets of members 19, 20 and 21 serve as struts provided with threaded extension devices capable of being tightened to firmly press the flanges of the die axially against the inner faces of the housing 5. The upper and lower halves of the spreader cage are held together by a locking spring 22.

FIG. 2 shows the same die structure as FIG. 1 but to larger scale. In FIG. 2 the closure member 12 of the housing 5 is shown as being screw threaded into the open end 6 of the housing although the closure member may be otherwise applied. In the form shown it is turned up tight against the die, a small standoff 23 being provided between the end face of the housing and the flange of the closure member to insure that the closure member will at all times bear against the die with optimum pressure.

FIG. 3 shows a modified form of die which comprises a plurality of die elements 8a and 8b which are arranged side by side in contact in the housing 5, each of the die elements 8a and 8b having a passage therethrough, such passages being coaxial but, as shown, of different cross-sectional dimensions to provide in efl'ect a composite passage through the die tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die. The dies are maintained in place in the housing by spreader cages 16a, one for each die, similar to the spreader cage 16 above described for the die 8. As in FIGS. 1 and 2, fluid under pressure is admitted through the pipe 13 and is exhausted through the pipe 14 and the conrtol valve 15.

FIG. 3 shows a tubular metal blank 3a being formed on a tapered mandrel 2a by the die elements 811 and 81:.

FIG. 4 is like FIG. 3 except that a partition 24 sealed to the inside of the housing 5 by an O ring 25 separates and segregates the die elements 8a and 8b and means are provided for applying and controlling fluid pressure separately to the respective die elements. In this figure fluid under pressure is admitted through the pipe 13a to both dies. The fluid is discharged through the pipe 14a but the discharge from each die element is controlled by a separate valve, valve 150 being provided for the die element 8a and a valve 15b being provided for the die element 8b. This: enables more precise control of the pressure exerted against the tubular metal blank as it is being formed into a tapered tube on the tapered mandrel.

While I have shown and described certain present preferred embodiments of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied Within the scope of the following claims.

I claim:

1. A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of non-metallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die when in repose having a passage therethrough tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die.

2. A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of non-metallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die when in repose having a passage therethrough tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die and having outwardly projecting flanges at its respective ends, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die.

3. A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of non-metallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die having a passage therethrough tapering from minimum cross section near one end of the die to maximum cross section near the opposite end of the die and having outwardly projecting flanges at its respective ends, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die, the flange at the larger end of the die having a greater transverse dimension than the flange at the smaller end of the die.

4. A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of non-metallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die having a passage therethrough tapering from minimum cross section near one end of the die to maximum cross section near the oposite end of the die and having outwardly projecting flanges at its respective ends, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die, the outside dimensions of the flanges being smaller than the inside dimensions of the housing opposite the flanges by at least about 6% of the maximum outside dimension of the flanges.

5. A die assembly as claimed in claim 1 in which the outside dimensions of the flanges are smaller than the inside dimensions of the housing opposite the flanges by at least abount 6% 0f the maximum outside dimension of the flanges.

6. A die assembly as claimed in claim 1 in which the outside dimension of the flange at the larger end of the die is smaller than the inside dimension of the housing opposite that flange by at least about 6% of the maximum outside dimension of the flanges and the outside dimension of the flange at the smaller end of the die is smaller than the inside dimension of the housing oposite that flange by at least about 8% of the maximum outside dimension of the flanges.

7. A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of non-metallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die comprising a plurality of die elements arranged side by side in contact each having a passage therethrough, the passages through the die elements being coaxial but of different cross-sectional dimensions to provide in effect a passage through the die tapering from minimum cross section near one end of the die to maximum cross section near the oposite end of the die, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die.

8. A die assembly for forming a tubular metal blank on a tapered mandrel into a tapered tube conforming to the taper of the mandrel comprising a die composed of non-metallic plastic material capable of being repeatedly stretched outwardly and contracted back to its original form, the die having a passage therethrough and having outwardly projecting flanges at its respective ends, a housing in which the die is mounted, means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the tubular metal blank and mandrel pass through the die and mechanical means spanning the space between the flanges pressing the flanges generally axially of the die assembly against the housing to prevent leakage of pressure fluid between the flanges and the housing.

9. A die assembly as claimed in claim 8 in which spaced apart struts are provided which extend generally axially of the die assembly between the flanges to press the flanges against the housing.

10. A die assembly as claimed in claim 9 in which the struts are longitudinally extensible to enable them to exert a controlled degree of presure against the flanges.

11. A die assembly as claimed in claim 10 in which the struts are provided with threaded extension devices.

12. A die assembly as claimed in claim 9 in which hollow presure transmitting members lie against the flanges and the struts apply pressure against such members.

13. A die assembly as claimed in claim 7 including means for applying and controlling fluid pressure separately to the respective die elements.

References Cited UNITED STATES PATENTS 3 /1971 Matthews 72-276 8/ 1971 Cress 72283 9/ 1895 Thackray 72-468 8/1939 Lemming 72283 8/1942 Strock 72-274 4/1966 Green 72-468 U.S. Cl. X.R. 

